﻿using System;
using static ClHcaSharp.Constants;

namespace ClHcaSharp
{
    internal static class Ath
    {
        private static readonly byte[] baseCurve = new byte[656]
        {
            0x78, 0x5F, 0x56, 0x51, 0x4E, 0x4C, 0x4B, 0x49, 0x48, 0x48, 0x47, 0x46, 0x46, 0x45, 0x45, 0x45,
            0x44, 0x44, 0x44, 0x44, 0x43, 0x43, 0x43, 0x43, 0x43, 0x43, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42,
            0x42, 0x42, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x40, 0x40, 0x40, 0x40,
            0x40, 0x40, 0x40, 0x40, 0x40, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
            0x3F, 0x3F, 0x3F, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3D, 0x3D, 0x3D, 0x3D, 0x3D, 0x3D, 0x3D,
            0x3C, 0x3C, 0x3C, 0x3C, 0x3C, 0x3C, 0x3C, 0x3C, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B,
            0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B,
            0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3B, 0x3C, 0x3C, 0x3C, 0x3C, 0x3C, 0x3C, 0x3C, 0x3C,
            0x3D, 0x3D, 0x3D, 0x3D, 0x3D, 0x3D, 0x3D, 0x3D, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3E, 0x3F,
            0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
            0x3F, 0x3F, 0x3F, 0x3F, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40,
            0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41,
            0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41,
            0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42,
            0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x43, 0x43, 0x43,
            0x43, 0x43, 0x43, 0x43, 0x43, 0x43, 0x43, 0x43, 0x43, 0x43, 0x43, 0x43, 0x43, 0x43, 0x44, 0x44,
            0x44, 0x44, 0x44, 0x44, 0x44, 0x44, 0x44, 0x44, 0x44, 0x44, 0x44, 0x44, 0x45, 0x45, 0x45, 0x45,
            0x45, 0x45, 0x45, 0x45, 0x45, 0x45, 0x45, 0x45, 0x46, 0x46, 0x46, 0x46, 0x46, 0x46, 0x46, 0x46,
            0x46, 0x46, 0x47, 0x47, 0x47, 0x47, 0x47, 0x47, 0x47, 0x47, 0x47, 0x47, 0x48, 0x48, 0x48, 0x48,
            0x48, 0x48, 0x48, 0x48, 0x49, 0x49, 0x49, 0x49, 0x49, 0x49, 0x49, 0x49, 0x4A, 0x4A, 0x4A, 0x4A,
            0x4A, 0x4A, 0x4A, 0x4A, 0x4B, 0x4B, 0x4B, 0x4B, 0x4B, 0x4B, 0x4B, 0x4C, 0x4C, 0x4C, 0x4C, 0x4C,
            0x4C, 0x4D, 0x4D, 0x4D, 0x4D, 0x4D, 0x4D, 0x4E, 0x4E, 0x4E, 0x4E, 0x4E, 0x4E, 0x4F, 0x4F, 0x4F,
            0x4F, 0x4F, 0x4F, 0x50, 0x50, 0x50, 0x50, 0x50, 0x51, 0x51, 0x51, 0x51, 0x51, 0x52, 0x52, 0x52,
            0x52, 0x52, 0x53, 0x53, 0x53, 0x53, 0x54, 0x54, 0x54, 0x54, 0x54, 0x55, 0x55, 0x55, 0x55, 0x56,
            0x56, 0x56, 0x56, 0x57, 0x57, 0x57, 0x57, 0x57, 0x58, 0x58, 0x58, 0x59, 0x59, 0x59, 0x59, 0x5A,
            0x5A, 0x5A, 0x5A, 0x5B, 0x5B, 0x5B, 0x5B, 0x5C, 0x5C, 0x5C, 0x5D, 0x5D, 0x5D, 0x5D, 0x5E, 0x5E,
            0x5E, 0x5F, 0x5F, 0x5F, 0x60, 0x60, 0x60, 0x61, 0x61, 0x61, 0x61, 0x62, 0x62, 0x62, 0x63, 0x63,
            0x63, 0x64, 0x64, 0x64, 0x65, 0x65, 0x66, 0x66, 0x66, 0x67, 0x67, 0x67, 0x68, 0x68, 0x68, 0x69,
            0x69, 0x6A, 0x6A, 0x6A, 0x6B, 0x6B, 0x6B, 0x6C, 0x6C, 0x6D, 0x6D, 0x6D, 0x6E, 0x6E, 0x6F, 0x6F,
            0x70, 0x70, 0x70, 0x71, 0x71, 0x72, 0x72, 0x73, 0x73, 0x73, 0x74, 0x74, 0x75, 0x75, 0x76, 0x76,
            0x77, 0x77, 0x78, 0x78, 0x78, 0x79, 0x79, 0x7A, 0x7A, 0x7B, 0x7B, 0x7C, 0x7C, 0x7D, 0x7D, 0x7E,
            0x7E, 0x7F, 0x7F, 0x80, 0x80, 0x81, 0x81, 0x82, 0x83, 0x83, 0x84, 0x84, 0x85, 0x85, 0x86, 0x86,
            0x87, 0x88, 0x88, 0x89, 0x89, 0x8A, 0x8A, 0x8B, 0x8C, 0x8C, 0x8D, 0x8D, 0x8E, 0x8F, 0x8F, 0x90,
            0x90, 0x91, 0x92, 0x92, 0x93, 0x94, 0x94, 0x95, 0x95, 0x96, 0x97, 0x97, 0x98, 0x99, 0x99, 0x9A,
            0x9B, 0x9B, 0x9C, 0x9D, 0x9D, 0x9E, 0x9F, 0xA0, 0xA0, 0xA1, 0xA2, 0xA2, 0xA3, 0xA4, 0xA5, 0xA5,
            0xA6, 0xA7, 0xA7, 0xA8, 0xA9, 0xAA, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAE, 0xAF, 0xB0, 0xB1, 0xB1,
            0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF,
            0xC0, 0xC1, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD,
            0xCE, 0xCF, 0xD0, 0xD1, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB, 0xDC, 0xDD,
            0xDE, 0xDF, 0xE0, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA, 0xEB, 0xED, 0xEE,
            0xEF, 0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF7, 0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFF, 0xFF
        };

        public static byte[] Init(int type, int sampleRate)
        {
            return type switch
            {
                0 => Init0(),
                1 => Init1(sampleRate),
                _ => throw new ArgumentException("Invalid ATH type."),
            };
        }

        private static byte[] Init0()
        {
            byte[] athCurve = new byte[SamplesPerSubframe];
            for (int i = 0; i < athCurve.Length; i++)
            {
                athCurve[i] = 0;
            }

            return athCurve;
        }

        private static byte[] Init1(int sampleRate)
        {
            byte[] athCurve = new byte[SamplesPerSubframe];
            int acc = 0;

            for (int i = 0; i < athCurve.Length; i++)
            {
                acc += sampleRate;
                int index = acc >> 13;

                if (index >= 654)
                {
                    Fill<byte>(athCurve,  i, SamplesPerSubframe - i,0xFF);
                    break;
                }
                athCurve[i] = baseCurve[index];
            }

            return athCurve;
        }

        public static void Fill<T>(T[] array, int start, int end, T value)
        {
            if (array == null)
            {
                throw new ArgumentNullException("array");
            }
            if (start < 0 || start >= end)
            {
                throw new ArgumentOutOfRangeException("fromIndex");
            }
            if (end >= array.Length)
            {
                throw new ArgumentOutOfRangeException("toIndex");
            }
            for (int i = start; i < end; i++)
            {
                array[i] = value;
            }
        }
    }
}